copper(II) polyamine chelates as efficient receptors for acyclovir: syntheses, crystal structures and dft study

In order to further understand the metal-binding patterns (MBP) of acyclovir (acv), copper(II) and zinc(II) oxo salts (nitrate, sulfate or perchlorate) and tridentate or tripodal-tetradentate chelating-polyamines were reacted with acyclovir to obtain the following compounds: [Cu(dien)(acv)(H2O)]SO4 center dot 1.25MeOH center dot 0.5H(2)O (1), [Cu(dien)(acv)(H2O)]center dot[Cu(dien)(acv)(H2O)(NO3)](NO3)(3)]center dot H2O (2), {[Cu(dien)(mu(2)-acv)](ClO4)(2)}(n) (3), [Zn(dien)(acv)(SO4)] (4), [Cu(pmdta)(acv)](ClO4)(2)center dot H2O (5), [Cu(bpa)(acv)(SO4)]center dot 6H(2)O (6), [Cu(tren)(acv)](NO3)(2) (7) and [Cu(tren)(acv)](ClO4)(2) (8) (dien = diethylenetriamine, pmdta = N,N,N',N',N"-pentamethyl-diethylenetriamine, bpa = bis-(2-picolyl)amine and tren = tris(2-aminoethyl)amine). All the compounds were studied by spectroscopic techniques and single-crystal X-ray diffraction methods. The metal binding pattern of copper(II) compounds 1-3, 7 and 8 consists of the cooperation of the Cu-N7(acv) bond with an intramolecular interligand (primary/terminal amino)N-H center dot center dot center dot O-6(acv) interaction (which is bifurcated in 8). Note that in 3 this MBP is embedded within the unusual bridging mu(2)-N7,O(ol, N9-side chain) mode. On the other hand, the Zn-N7(acv) bond in compound 4 is reinforced with the intramolecular (secondary amino)N-H center dot center dot center dot O6(acv) H-bond. This latest interaction is indeed possible but not displayed in compounds 5 or 6, which feature an asymmetric chelating-N7,O6-acv MBP with O6 acting as an apical/distal Cu(II) donor atom. Remarkably, in compounds 7 and 8, an intricate combination of anion...pi/pi...pi/pi...anion interactions generates interesting supramolecular networks that have also been studied theoretically by means of DFT calculations. In addition, these assemblies have been characterized using Bader's theory of "atoms-in-molecules". (C) 2018 Elsevier Ltd. All rights reserved.